1. Field
One or more exemplary embodiments relate to a tomography imaging apparatus and a method of reconstructing a tomography image, and more particularly, to a tomography imaging apparatus for reconstructing a tomography image by performing a tomography scan on a moving object and a method of reconstructing a tomography image therefor.
2. Description of the Related Art
Medical imaging apparatuses are used to acquire images showing an internal structure of an object. The medical imaging apparatuses are non-invasive examination apparatuses that capture and process images of details of structures, tissue, fluid flow, etc., inside a body and provide the images to a user. A user, e.g., a medical practitioner, may use medical images output from the medical imaging apparatuses to diagnose a patient's condition and diseases.
A tomography apparatus is a representative example of an apparatus for photographing an object by emitting X-rays toward a patient. In detail, a computed tomography (CT) apparatus may be an example of a tomography imaging apparatus.
Among medical image processing apparatuses, a CT apparatus is capable of providing a cross-sectional image of an object. Furthermore, the CT apparatus may represent an internal structure (e.g., organs such as a kidney, a lung, etc.) of the object without superimposing images, as compared to a general X-ray apparatus. Due to these advantages, a CT apparatus has been widely used for precise diagnosis of diseases. A medical image acquired by a tomography imaging apparatus is hereinafter referred to as a tomography image. In detail, a medical image acquired by a CT apparatus is referred to as a CT image.
To obtain a tomography image, a tomography imaging apparatus performs a tomography scan of an object to acquire raw data. The acquired raw data is used to reconstruct a tomography image. In this case, the raw data may be projection data obtained by projecting an X-ray onto the object or a projection data set called a sinogram.
For example, to obtain a CT image, image reconstruction may have to be performed using raw data obtained by performing a CT scan.
In detail, a CT scan is performed as an X-ray source included in a CT apparatus rotates around an object, and raw data is acquired from the CT scan. To produce a cross-sectional CT image, to acquire raw data, the X-ray source has to rotate by an angle that is greater than or equal to 180 or 360 degrees. If one period is defined as the time required to acquire raw data needed for reconstructing one cross-sectional CT image, one period in a general CT apparatus is greater than or equal to 0.2 seconds.
If an object to be scanned moves quickly, motion of the object may occur even during one period. Due to the motion of the object, motion artifacts may occur during reconstruction of a CT image.
Furthermore, a 3D CT image may be reconstructed using a plurality of cross-sectional CT images. Thus, motion of an object may occur very frequently during acquisition of raw data necessary for reconstructing a 3D CT image.
When motion artifacts occur, boundaries of an object in a reconstructed CT image may appear blurred, or a reconstructed image may be unclear. Thus, motion artifacts introduced in a CT image reduce the quality of the CT image and accordingly, degrade the accuracy of analysis of an image and diagnosis of a disease by a user, e.g., a medical practitioner.
Thus, for a CT scan of a moving object, it is of paramount importance to reconstruct a CT image having minimized motion artifacts.